Solar panel with mat base member

ABSTRACT

A solar panel including photovoltaic cell encapsulated in a silicone resin, in which the base member to which the silicone resin adheres is a glass mat polyester in laminate or molded form.

The present invention relates generally to enclosures, such as trays andframes, for holding photovoltaic cells in position so that incidentlight may impinge upon the surface of the cells, thereby generatingelectrons that can, by suitable means, be directed away from the cellsand stored or utilized directly. More particularly, the presentinvention is directed to such a solar panel in which one or more cellsare encapsulated in a substantially transparent resin so that the cellsare protected from ambient conditions that would otherwise bedeleterious to the function of the cells.

In making the present invention, I have been made aware of two priorapplications that are presently pending before the U.S. Patent andTrademark Office. Each has been assigned to Solarex Corporation, ofRockville, MD., the assignee of the present application. On eachapplication, Joseph Lindmayer is the named inventor. Each applicationrelates to a solar panel in which solar cells are encapsulated in aresin, most preferably a silicone resin. When the panel is located wherelight will impinge on it, the solar cells that are encapsulated in the.[.resing.]. .Iadd.resin .Iaddend.will be protected from hail, rain,dirt and like conditions but maintained in position so that they willgenerate electricity upon being subjected to radiant energy. Thus, inapplication Ser. No. 715,407, filed Aug. 25, 1976 and entitled, SolarPanel, now U.S. Pat. No. 4,057,439 Dr. Lindmayer disclosed a panelhaving solar energy cells encapsulated therein in which two differentresins were utilized. As pointed out in that patent application, oneproblem that has been present in such solar cell panels, which are to beexposed to heat and light, is delamination from the normally flat bottomof the panel. The invention described in this patent application didassist in substantially reducing such delamination.

Still another article of manufacture in which delamination of a siliconeor other resin from a base member of a solar panel has been inhibited isdisclosed in U.S. application Ser. No. 806,868, filed June 15, 1977, nowU.S. Pat. No. 4,093,473 and entitled, Solar Panel with UV Absorber, onwhich Dr. Lindmayer is also the named inventor. Based on the discoverythat delamination may, at least in part, be due to the incidence ofultraviolet light on the area of surface contact of the resin and thebase member of the solar panel, Dr. Lindmayer then determined that theuse of a type of absorber of ultraviolet light in the silicone resinwould likewise assist in mitigating this problem. Delamination, i.e.,separation of the resin from the normally flat bottom or base member ofthe tray or other receptacle in which the resin is placed, can render asolar panel inoperative. Even if it does not render the panelinoperative, delamination can cause the panel to become unsightly andwill reduce the amount of radiant energy impinging on one or more cellsby varying the angle at which incident light strikes the cells.

It is, therefore, the primary object of the present invention to providea substrate or base member for a solar panel for photovoltaic cells inwhich delamination of the resin from the base member is mitigated.

I have accomplished this object by utilizing a substrate alone, or asthe base member for the panel, tray, or other receptacle for solarcells, a stable, insulating, glass mat polyester laminate. Such a mat isresistant to warpage at temperatures of about 150° to 200° C. and iscompatible with the silicone or other resin used. Further, the glass mathas an upwardly facing surface that is in contact with the siliconeresin and is formed with alternating peaks and valleys, and thepeak-to-valley dimension is less than about 0.01 inch. In this manner, Ifind that I have achieved improved adherence of the silicone or otherresin to the base member of the panel and thereby retarded delaminationunder adverse ambient conditions.

In more restricted embodiments of my invention, the peak-to-valleydimension is about 0.002 to 0.004 inch, most preferably 0.004 inch. Mosteasily, such peak-to-valley dimension can be formed by sanding theupwardly facing surface of the base member. Although it may be moreexpensive to provide a glass mat polyester laminate that is flameretardant, that will be an improved characteristic of the base member.

Most advantageously, the mat polyester laminate that forms the basemember of a tray according to my invention, is utilized in conjunctionwith a solar panel having a structure as disclosed by Dr. Lindmayer inhis application Ser. No. 715,407. Consequently, in such preferredembodiment, there will be a tray or other receptacle with a glass matpolyester laminate as the base member. A body of resin is composed of alayer of single-component silicone resin that will be in direct contactwith the upwardly facing surface of the base member and adhered thereto,and a layer of multi-component silicone resin will overlay and beadhered to that single-component layer, the multi-component layer beingthicker than the single-component layer and encapsulating photovoltaiccells there within. Indeed, it is also preferable to employ anultraviolet light absorber, at least in the multi-component layer, allaccording to the two patent applications of Dr. Lindmayer referred tohereinbefore.

As has been disclosed in the prior Lindmayer applications, theconventional base member that had been used to form a solar panel is onemade of epoxy fiberglass. That surface is smooth, having substantiallyno peaks and valleys. Such epoxy fiberglass cloths have developedseveral substantial difficulties in usage. Thus, at processingtemperatures prior to addition of silicone resin, they tend to warp,i.e., at 150° to 200° C. temperatures there is warpage. Further, at suchtemperatures color changes occur, e.g., the normally white or creamcolored board tends to turn brown. A polyester mat, on the other hand,has been found to have minimal deformation at 200° C. and minimaldiscoloration. In addition, the smooth surface of the fiberglass boardis difficult to adhere any resin to; consequently, it is difficult toprime the upwardly facing surface of a fiberglass board, anddelamination occurs in processing, i.e., curing of the resin, as well asin the field. Moreover, epoxy fiberglass base members have a tendencyfor the epoxy resin to decompose during exposure to ultraviolet light,whereby the base member develops a chalking on the outside of thefiberglass. This chalking aggravates water absorption by individualfibers of the glass substrate, which are exposed and thereafter act aswicks to carry water from external surfaces of the base member throughthe base member and into contact with the silicone resin conterminoustherewith. Such moisture accelerates the delamination process.

In the preferred embodiment of my invention, I utilize a glass matpolyester laminate as the base member of a solar panel, which mat issold by the Glastic Corporation of Cleveland, Ohio, under the trademarkGlastic 200. The mat may have a thickness preferably between 1/16 and1/8 inch, with 3/32 inch being preferred. More specifically, theupwardly facing surface of the mat has alternating peaks and valleysand, most preferably, the peak-to-valley dimension is 0.004 inch. Suchalternating peaks and valleys are achieved by sanding the upwardlyfacing mat surface in such manner as will be apparent to those of skillin this art. Although more expensive, a mat polyester laminate that isflame retardant, such as Glastic 200 FR may be substituted. Also, a UVinhibitor may be incorporated in the mat.

With respect to the specific structure of a solar panel in which thebase member of the present invention is utilized, reference is made tosaid application Ser. No. 715,407, which is incorporated herein byreference where necessary. Where it is required, said other Lindmayerapplication filed June 15, 1977, is also incorporated by reference.

Several other base member compositions, in addition to epoxy fiberglass,have been found to be markedly inferior to the polyester mat that hasbeen found to be successful in resisting delamination from a siliconeresin layer. Thus, resins in the form of board with paper embeddedtherein have not been successful. Ureaformaldehyde resins have beenfound decidedly inferior, as are polyvinyl chloride boards. Stillfurther, epoxy fiberglass is not readily capable of being sanded andthereby being formed with an upwardly facing surface with alternatingpeaks and valleys. This is because fiberglass is an impregnated cloth,whereas the polyester mat that I have found to be far superior in termsof resistance to delamination is a mat with random fibers. A mat ofrandom fibers is less susceptible to wicking. Therefore, delamination isnot accelerated by moisture brought to the base member-resin interfacewhich often occurs when cloth is utilized. With random fibers, anymoisture that wicks into fibers at the outside of the board or mat willnot be directed through the mat but, according to the arrangement of thefibers, will usually remain within the interior of the mat, and moisturewill thus not be wicked into the interior of the solar panel. Further,it is not advantageous to attempt to form a surface with peaks andvalleys when a cloth is utilized as a base member, since sanding willnecessarily expose fibers of the cloth. Such exposure of fibers mayseriously weaken the cloth and also aggravate wicking directly to thecloth-resin interface. Moreover, a glass mat polyester can either belaminated or molded, whereas epoxy fiberglass can only be obtained insheet form.

It will be apparent to those of skill in this art that certainalterations, modifications and substitutions may be made in thepreferred embodiment of the present invention disclosed herein. Forexample, while a mat containing a polyester laminate having relativelylong chains, such as is exemplified by Glastic 200, is most preferred,laminates formed from polyester resins having shorter chains are useful,although most certainly not preferred. As to all such alterations,modifications and substitutions, it is intended that they be includedwithin the scope of the present invention, which is to be limited onlyby the scope, including equivalents, of the following, appended claims.

I claim:
 1. A solar panel which maintains solar energy cells in position to receive light impinging thereon, comprising a base member having an upwardly facing surface with respect to the source of light, of body of cured silicone resin adhesively adhered to said upwardly facing surface, and photovoltaic cells disposed within and encapsulated by said body of resin so that said cells are maintained by said panel in position to receive light impinging on surfaces thereof and convert such light into electrical energy while being protected from ambient conditions by said body of resin, wherein said base member is formed from an.[.,.]. insulating, glass mat polyester that is resistant to warpage at temperatures of about 150° to 200° C. said upwardly facing surface of said base member being formed with alternating peaks and valleys in which the peak-to-valley dimension is less than about 0.01 inch to improve adherence of said body of resin to said mat and retard delamination under adverse ambient conditions.
 2. A solar panel as claimed in claim 1, in which said peak-to-valley dimension is about 0.002 to 0.004 inch.
 3. A solar panel as claimed in claim 2, in which said peak-to-valley dimension is about 0.004 inch.
 4. A solar panel as claimed in claim 1, in which said glass mat polyester is flame retardant.
 5. A solar panel as claimed in claim 1, in which said glass mat polyester is in the form of a laminate.
 6. A solar panel which maintains solar energy cells in position to receive light impinging thereon, comprising a tray within which said cells are mounted, said tray including side and end members and a base member having an upwardly facing surface within the space bounded by said tray, a layer of cured single-component silicone resin adhesively adhered to said upwardly facing surface, a layer of cured multi-component silicone resin adhered to said single-component layer, said single-component layer being thinner than said multi-component layer, and photovoltaic cells disposed within and encapsulated by said multi-component layer so that said cells are maintained by said panel in position to receive light impinging on surfaces thereof and convert such light into electrical energy while being protected from ambient conditions by said multi-component layer of resin, said base member being formed from an.[.,.]. insulating glass mat polyester that is resistant to warpage at temperatures of about 150° to 200° C.
 7. A solar panel as claimed in claim 6, in which said upwardly facing surface of said base member is formed with alternating peaks and valleys in which the peak-to-valley dimension is less than about 0.01 inch to improve adherence of said single-component layer to said mat and retard delamination under adverse ambient conditions.
 8. A solar panel as claimed in claim 7, in which said upwardly facing surface is formed by sanding and said peak-to-valley dimensions is about 0.002 to 0.004 inch. .Iadd.
 9. A solar panel which maintains solar energy cells in position to receive light impinging thereon, comprising a base member having an upwardly facing surface with respect to the source of light, a body of cured silicone resin adhesively adhered to said upwardly facing surface, and photovoltaic cells disposed within and encapsulated by said body of resin so that said cells are maintained by said panel in position to receive light impinging on surfaces thereof and convert such light into electrical energy while being protected from ambient conditions by said body of resin, wherein said base member is formed from an insulating, glass mat polyester that is resistant to warpage at temperatures of about 150° to 200° C. .Iaddend. .Iadd.10. A solar panel as claimed in claim 9, in which said glass mat polyester is flame retardant. .Iaddend. .Iadd.11. A solar panel as claimed in claim 9, in which said glass mat polyester is in the form of a laminate..Iaddend. 